class Compiler {
  constructor(vm) {
    this.el = vm.$el
    this.vm = vm
    this.compile(this.el)
  }

  //编译模板，处理文本节点和元素节点
  compile(el) {
    let childNodes = el.childNodes;
    Array.from(childNodes).forEach(node => {
      if(this.isTextNode(node)) {
        this.compileText(node)
      }else if(this.isElementNode(node)) {
        this.compileElement(node)
      }

      if(node.childNodes &&node.childNodes.length) {
        this.compile(node)
      }
    })
  }

  //编译元素节点，处理指令
  compileElement(node) {
    Array.from(node.attributes).forEach(attr =>{
      let attrName = attr.name;
      if(this.isDirective(attrName)) {
        attrName = attrName.substr(2);
        let key = attr.value;
        this.update(node,key,attrName)
      }
    })
  }

  update(node, key, name) {
    let updateFn = this[name+'Updater']
    updateFn && updateFn.call(this,node,this.vm[key],key)
  }

  //处理v-text
  textUpdater(node,value,key) {
    node.textContent = value
    new Watcher(this.vm,key,(newValue) => {
      node.textContent = newValue
    })
  }

  //处理v-model
  modelUpdater(node,value,key) {
    node.value = value
    new Watcher(this.vm,key,(newValue) => {
      node.value = newValue
    })
    // console.log('s');
    node.addEventListener('input',()=> {
      this.vm[key] = node.value
    })
  }

  // 处理 v-html 指令
  htmlUpdater (node, value, key) {
    node.innerHTML = value
    new Watcher(this.vm, key, (newValue) => {
      node.innerHTML = newValue
    })
  }

  // 处理 v-on 指令
  onUpdater (node, value, key, eventType) {
    node.addEventListener(eventType, value)
    new Watcher(this.vm, key, newValue => {
      node.removeEventListener(eventType, value)
      node.addEventListener(eventType, newValue)
    })
  }

  //编译文本节点，处理插值表达式
  compileText(node) {
    let reg = /\{\{(.+?)\}\}/
    let value = node.textContent
    if(reg.test(value)) {
      let key = RegExp.$1.trim()
      node.textContent = value.replace(reg,this.vm[key])

      //创建watcher对象，当数据改变时，更改视图
      new Watcher(this.vm,key,(newValue) => {
        node.textContent = newValue
        console.log('ss');
      })
    }

  }

  //判断是否是指令
  isDirective(attrName) {
    return attrName.startsWith('v-')
  }

  //判断是否是文本节点
  isTextNode(node) {
    return node.nodeType===3
  }

  //判断是否是元素节点
  isElementNode(node) {
    return node.nodeType===1
  }
}
